The present exemplary embodiment relates to the measurement of flow of gases in various systems. It finds particular application in conjunction with detecting air flow velocity using Fast Fourier Transform and vortex shedding, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
Currently, air flow velocity measurement utilizes a fluid dynamics concept known as “Vortex Shedding” in order to determine the velocity of air flow within a duct. Specifically, a rigid object of a specific shape is placed within the flow. This object tends to create eddies in the flow as air passes around the object. These eddies create small periodic pressure differences which are transmitted down a plastic tube to a microphone where the energy in the pressure waves is converted to electrical energy by movement of a diaphragm due to air pressure changes. The current electrical hardware takes two microphones wired in anti-phase as an input. The two single-ended microphone signals are then treated as a differential signal, which is essentially band pass filtered by the combination of an AC coupling capacitor and a passive RC low pass filter. The signals are then fed into a differential amplifier where the signals are subtracted. Subsequent circuitry performs peak detection using sample and hold comparison and the result is a set of pulses of varying width which are averaged to produce a signal proportional to the rate of flow. The current electrical hardware configuration does not enable the digital processing of the electrical energy to detect air flow velocity and/or other further analysis. The present application eliminates the need for the current electrical hardware configuration.
The present application provides a new and improved system and method for detecting air flow velocity which overcomes the above-referenced problems and others.